The Galileo Affair, or a Baffling Road Toward Heliocentricism

The house arrest of Galileo Galilei in 1633 is commonly put forth as an example of how religion, and particularly the Catholic Church, is against scientific progression. The issue of science and religion in general deserves its own post (or many), but this specific example has gained its own unique spin.

What Happened – The Short Version

Galileo, one of the central movers of the Scientific Revolution, was repeatedly questioned by the Inquisition concerning his heliocentric theories, which it labeled heretical because it contradicted portions of the Bible. In 1633, he was put under indefinite house arrest for the publication of his most famous work, Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican, which was then added to the official Index of Forbidden Books.

Everything above is absolutely correct. It’s also over-simplified.

Wider Suspicions of Heliocentricism

Heliocentric theory was a contentious topic throughout Galileo’s lifetime. While one issue was that it ran contrary to literal readings of the Bible, another was the difficulty in proving it.

Evidence of a heliocentric universe was primarily mathematical in nature at a time when that wasn’t a means of proving something. If you wanted to understand the world you directly studied it (or you philosophized about it: there’s a reason scientists of the day were called natural philosophers), and by observance it seemed obviousthe heavenly bodies rotated around the earth.

As an Aside: You may find it odd, even backward, that 17th century people had difficulty accepting mathematical evidence. This is because we are used to that being a valid form of argument. The Scientific Revolution involved a complete paradigm shift in how people studied, examined and understood the world.

To give another example, in a significant portion of the Middle Ages, written documents held very little weight in legal disputes. Today, if I offer up a properly written and signed contract, the law immediately recognizes it. But back then it was a person’s word – and the word of others who stepped forth to swear in support of the person’s good character – that was most valued. Paper merely held anonymous words. Who knew who actually wrote it? Witnesses could be questioned. Documents could not. It was a very different perspective of the world than what we have today.

The Church didn’t merely make Biblical arguments. They made rational ones as well. There were plenty of natural philosophers who didn’t accept heliocentricism at the time. And how a heliocentric world worked wasn’t laid out until Sir Isaac Newton did it fifty years later in 1687.

Stunningly Poor Heliocentric Models

We hail those who put forth heliocentric theories because they set the stage for further developments in cosmic understanding. However, we tend to gloss over the fact that many of their ideas about the universe were still significantly, and often hilariously, wrong.

If you break down the cosmic views Nicolaus Copernicus, for example, you find an idea almost as flawed as the earth-centric view, including:

Circular orbits rather than elliptical ones

The sun being in the center of the universe, not merely the solar system.

The planets embedded within crystalline spheres rather than moving along orbital planes.

Epicycles, which are small orbits along larger orbits, used to explain why planets appear to speed up, slow down, and move backward.

A planet with a single epicycle. The red line traces the planet’s path as it rotates on both its deferent (the orbit around the earth or sun) and epicycle. Epicycles were commonly stacked on top of other epicycles. (Source)

Finally, Copernicus’s mathematical arguments only provided a theory of how things might work without real argument this was how things did work.

Tycho Brahe offered an even weirder solution: while the planets orbited the sun, the sun, moon and stars rotated around the earth.

Yeah, that totally makes more sense.

Neither was Galileo immune to errors. He continued to insist in circular orbits (even though Johannes Kepler had already put forth the idea of elliptical ones) and the centrality of the sun in the entire universe, which is really only minutely more correct than placing the earth at the center.

There were lots of perfectly good reasons why Church authorities found a lack of merit in heliocentric models. It was not a simple argument of “the Bible says so.”

The Arrogance of Galileo

In 1616, the Inquisition commanded Galileo to stop teaching and defending heliocentricism as truth. He was, however, able to continue dealing with it as a hypothetical mathematical model.

In 1623, Galileo’s friend Cardinal Maffeo Barberini because Pope Urban VIII. Urban, who disagreed with Galileo on the matter of heliocentricisn, requested Galileo produce an unbiased work that provided both sides of the argument.

Why Urban thought Galileo would produce such a piece without highlighting his view as correct escapes me. Galileo was kind of a dick; no one recognized Galileo’s brilliance as much as Galileo.

The result was the Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican, in which three fictional characters debate the issue.

So, to be clear, the Church gave formal permission for Galileo to write the Dialogue.

Galileo, being Galileo, couldn’t help himself. The Dialogue concluded that the Copernican (heliocentric) view was far superior to the Ptolemaic (earth-centeric) one. Worse, the character defending the traditional view was named Simplico, and, even worse, his arguments used quotes that came from the pope (who wanted his arguments included).

Galileo insisted the character was named after an ancient philosopher, but simplico can also mean simpleton, i.e. an idiot. Urban was not amused. Galileo once more went to trial for disobeying his previous sentence and was put under house arrest for the rest of his life.